This invention relates to guidewires and catheters used for angioplasty and atherectomy, and devices for intraluminal, ultrasound imaging.
Description of prior art
U.S. Pat. No. 4,794,931 issued to Yock on Jan. 3, 1989 cites a catheter apparatus, system and method of two-dimensional intraluminal ultrasonography combined with a rotating, cutting tool for atherectomy.
The invention described in this patent cites a catheter for atherectomy having an ultrasonic transducer, mounted on rotating atherectomy cutting tool.
The catheter presented in above the patent, although allowing for radial scanning, does not have the ability to view forward, beyond the distal tip of the catheter.
The rotating cutting tool to which the transducer is attached may subject to cutting forces as the tool cuts into a plaque in a stenosed vessel. Such cutting forces may deflect the tool and the transducer, which are attached to a flexible drive cable. This creates a potential for instability of the axis of rotation of the scanning element and thus affect the stability and quality of the image.
The catheter quoted in the referenced article has a rotating mirror element, which reflects an ultrasound beam from a stationary transducer, deflecting said beam into a direction perpendicular to the axis of the catheter.
This creates the potential for unstable geometry of the ultrasound beam deflection and collection system, and thus for producing an image of poor quality and consistency.
The above mentioned inventions present an interesting embodiment of catheters for intraluminal ultrasound imaging, but nevertheless suffer from a number of disadvantages, such as:
Large size and poor flexibility and thus an inability to access coronary vessels, and to scan in narrowly occluded areas of blood vessels. PA1 Inability to effectively combine the ultrasound imaging and general angioplasty catheter. PA1 Inability to assess the vessel diameter and choose the catheter size, without inserting imaging catheters. PA1 Necessity to insert a catheter for ultrasound imaging and then a second catheter for angioplasty, which means repeated trauma to the blood vessel. PA1 Inability to center catheter in the vessel if the vessel is larger than the outside diameter of the catheter sheath. PA1 (a) Having a small diameter and therefore the ability to enter coronary vessels and perform ultrasonic scans in the narrowly occluded areas. PA1 (a) Having the ability to inspect occluded areas of blood vessels, prior to insertion of the angioplasty catheter, thus providing information useful in selection of the catheter size. PA1 (c) Having no need for insertion of a special imaging catheter, prior to angioplasty, and thus reduction in patient trauma, and chances of damage to vessel walls. PA1 (d) Having a simple and inexpensive construction of imaging guidewire. PA1 (f) Conforming to a well established standard shape and size of angioplasty guidewires. PA1 (h) Having an ability to be held in a central lumen of angioplasty catheter and held there to be activated at any time during angioplasty procedure. PA1 (i) Having the transducer located forward of the angioplasty balloon thus, in an angioplasty of narrow occlusions, having an ability to scan through occluded areas in front of the catheter and then following it with an angioplasty balloon.